Polyvinyl chloride (PVC) based tubing is used in numerous medical products. However, PVC is viewed as hazardous to both the environment and to personal health. Incineration of PVC results in the release of hydrochloric acid (HCl), and PVC is viewed as a major contributor to HCl in incinerator flue gases. Also, PVC is suspected of contributing to polychlorinated dibenzodioxin and furan toxins formed during incineration. Levels of these toxins are up to three times greater in medical infectious waste as compared to municipal waste streams. In addition to incineration concerns, exposure to di-2-ethylhexyl phthalate (DEHP), a common plasticizer used with PVC, may present a number of health related concerns, including reduced blood platelet efficacy and potential links to liver cancer.
Despite these concerns, PVC-based tubing and articles constructed therefrom, continue to be the material of choice in scientific and medical applications. See, e.g., Encyclopedia of Polymer-Science and Technology, Vol. 17, pg. 50 (1989). The continued use of PVC materials is due, at least in part, to PVC's attractive qualities, including flexibility; toughness; resistance to UV light, solvents, cuts, scratches, and acids; clarity or opaqueness as required; and low cost. In addition, PVC's properties can be modified through the addition of various additives, such as plasticizers, colorants, and the like. For example, U.S. Pat. No. 4,298,714 discloses a modified PVC material with reduced hydrophilicity due to the addition of various thiol-group compounds to the PVC backbone.
Other thermoplastic polymers have been used to form single-layer tubing. For example, low-density polyethylene, high density polyethylene, polypropylene, ethylene vinyl acetate, and polybutylene have all been used to form single-layer tubings. See, e.g., Encyclopedia of Polymer Science and Technology, Vol. 17, pp. 50-51 (1989). However, none of these polymer materials has been successfully used to provide tubing with the advantageous properties needed to serve as an environmentally compatible replacement for PVC-based materials.
Multilayered tubing which utilizes different polymers in the respective layers has also been developed. Specifically, such a multilayered tubing allows the bonding together of previously incompatible materials, such as PVC and ethylene vinyl acetate copolymer (EVA). For example, U.S. Pat. No. 4,707,389 discloses a multilayered tube composed of an outer layer of EVA and an inner layer of PVC, bonded together by a bonding layer. In addition to continued environmental incompatibility, this tubing tends to delaminate during continuous usage. To avoid delamination problems, U.S. Pat. No. 3,561,493 provided a multilayered tubing in which the inner and outer layers are welded together by a precompounded layer of the two different polymers. However, chlorine-containing polymers, such as PVC, are still considered for use in such tubings.
To date, no multilayered tubing exists which provides the advantageous characteristics of PVC materials, and yet is free of leachable contaminants and is environmentally compatible.
Therefore, there is a need for an environmentally compatible multilayered tubing that can be utilized in a wide range of both medical and nonmedical products, and that can serve as a replacement for PVC-based materials. Specifically, there is a need for PVC replacement tubing that would be both flexible, kink-resistant, and tough (i.e., scratch- and cut-resistant), as well as solvent and UV light resistant, clear or opaque as need be, and could be made for a relatively low cost.